In This Forest, a Clean Bill of Health Comes with Blue Polka-Dot Salamanders

To keep an invasive plant from poisoning amphibians, Illinois conservationists are cutting and burning the dreaded buckthorn.

May 04, 2016

Early-spring sleet pelts my face and eyelids as I turn over a log and scan the mud beneath it. It takes me a moment, but then I see what I came for. Its shiny skin and azure dots are unmistakable: a blue-spotted salamander.

Cecil Hynds-Riddle holding a salamander
Susan Cosier

I mark my find on a snow-splotched clipboard and replace the log, careful not to crush my quarry. The salamander is one of nearly a dozen I’ve seen so far today in Somme Woods, a forest preserve outside Chicago. Each of the three other volunteers in my group have found about as many—and that’s just in the vicinity of Big Marsh, a single pond.

We’re here counting salamanders for an amphibian monitoring project led by Karen Glennemeier, a conservation ecologist at Chicago’s Shedd Aquarium, with the help of the volunteer group Habitat 2030 and the Forest Preserve District of Cook County. Somme Woods is part of a 69,000-acre network of forest preserves set aside for protection back in 1914. A lot has changed since then, and the amphibians we find here will tell us how healthy the local ecosystem is: The more salamanders we see, the better the prognosis.

Buckthorn family (Rhamnaceae)
John M. Randall, The Nature Conservancy

Over the last century, the preserves have escaped development, but not the creep of invasive species—especially buckthorn. Originally from Europe, buckthorn takes over the understory of oak woodland, savanna, and prairie ecosystems. Here in Illinois it’s been running amok in these woods, and as it does, it poisons ponds and their amphibian inhabitants.

According to a 2014 study published in the Journal of Herpetology, buckthorn emits emodin, a deadly compound that stops frog embryos from developing. Its leaves also prevent sunlight from reaching algae and aquatic plants that need the light to produce the oxygen that tadpoles and salamander larvae breathe. Buckthorn’s low, dense branches also crowd out native plants, while its roots suck up water from the ground like straws, causing ponds to shrink or dry up quickly. A parched pond bed is no place for a clutch of amphibian eggs.

Keeping buckthorn at bay may also be important in keeping frogs and salamanders infected with chytrid fungus healthy. Although roughly 60 percent of amphibians in the United States test positive for chytrid, few die from it. Stressors like habitat fragmentation and destruction, pollution, and climate change, however, can make them more vulnerable, says Christopher Phillips, a herpetologist at the Illinois Natural History Survey. “It’s always best to have a healthy population, if you’re going to resist some new disease,” he says.

Somme Woods Forest Preserve, Northbrook Illinois
Urban Woodswalker/Flickr

To repair the damage wrought by buckthorn in Somme Woods and the other preserves, every year for the past two decades volunteers with the Cook County Forest Preserve District have waged war against the weedy invader by cutting it back, organizing controlled burns, and reseeding areas with native plants. Glennemeier’s amphibian monitoring project is trying to determine whether these restoration efforts are working. Healthy ponds where blue-spotted salamanders, spring peepers, and cricket frogs thrive are just one sign that they are.

Judging from the dozens of slowpoke salamanders (they’re cold-blooded, after all) my group spotted around Big Marsh—an area volunteers began restoring twenty years ago—the ecosystem seems to be doing well. But not every pond has seen as much love. As we make our way to a second pond surrounded by woods—which Cecil Hynds-Riddle, a community organizer, told us saw a controlled burn last fall—we count just a handful of salamanders. Though the fire killed a lot of buckthorn, volunteers have more work to do. Some of the shrubby, resilient invaders still stand, and their effect is evident.

Somme Woods Forest Preserve, Northbrook Illinois
Urban Woodswalker/Flickr

We wrap up the survey and trudge back through the forest to the parking lot, our boots squishing in the mud. Once everyone has regrouped, we discuss our findings: more salamanders in areas where volunteers have done the most work, something Glennemeier and Hynds-Riddle expect the data will continue to confirm. If they do, the surveys could lead to more widespread restoration efforts, healthier amphibian habitat, and more azure dots wriggling into the soft, brown earth next spring.


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